One of the odder moments of the Christmas narrative — often left out of pageants and children’s storybooks — is when Mary encounters Simeon at the temple. He is described as a devout man, but he is not a particularly cheery one. “This child is destined to cause the falling and rising of many in Israel,” Simeon tells Mary. “And a sword will pierce your own soul, too.”

This bit of biblical foreshadowing points to an uncomfortable implication of the incarnation. In the Christian story, God arrived, against all expectation, with shocking weakness and vulnerability. Whatever else humanness may signify, it means mortality. It is about six miles from Bethlehem to Golgotha — a short trip from crib to cross.

These are admittedly dark thoughts in a season of light. But many of us come to the holidays with pierced souls. My mother died recently and suddenly. She was artistic, restless and unfailingly kind. One week she was a lively voice on the phone. The next, her children were using the last cash in her wallet for dinner, in one final treat. In old photographs, taken in the 1950s when my father was stationed in Europe, she is impossibly young and beautiful — stylishly dressed, in sunglasses, smoking a cigarette, like Bette Davis on holiday. It is hard to imagine her in the cold ground.

The loss of parents brings a particular kind of loneliness. An emotional backstop is removed. The world seems immense and empty. No matter what I did in life — no matter what trouble I had earned or caused — my mother would always take my side. I won’t be loved that way again.

People who have recently lost a parent — or a spouse, or a friend, or (God forbid) a child — are easily ambushed by sorrow at this time of year. Psychologists have a term for it: “holiday effects.” A smell, a taste, a quality of light can cause grief to come in little chilly blasts. Traditions and family celebrations can be cruel reminders of absence.

For me, the proper description is probably “poignancy.” My best Christmas memories are now tinged by loss — yellowed and aged at the edges. The image in my mind, probably from about age 7 or 8 — of snow outside the front window, of a green couch, of a tree with tinsel, of invincible protection and warmth — is so long ago and far away. There are now no Mom and Dad to come down the stairs to. The exile is permanent.

But Christmas is not about mere nostalgia and not without its comforts. The British author J.R.R. Tolkien — something of an expert on such things — argued that every great fairy story has a “turn” in which despair is suddenly and miraculously reversed and the heart’s desire is fulfilled. “It denies (in the face of much evidence if you will) universal final defeat . . . giving a fleeting glimpse of Joy, Joy beyond the walls of the world, poignant as grief.” For Tolkien, this moment “rends . . . the very web of story” and allows us to see something real about the universe itself.

For Christians, the nativity story is the “turn” of human events. In a world that would not yield a bed to a pregnant woman, the miraculous reversal arrives in a manner no one expected. All involved are ambushed by hope. The very strangeness of the deliverance — involving angels, kings and a pregnant virgin — indicates that God alone has taken hold of the story line. There is a glimpse of joy beyond the walls of the world. But this narrative — which culminates every good fairy tale — is different. “Art has been verified,” claimed Tolkien. “Legend and History have met and fused.”

“There is no tale ever told that men would rather find was true,” Tolkien said, “and none which so many skeptical men have accepted as true on its own merits.” And what if it is true? Even when — in the midst of grief or suffering — it cannot be a source of happiness, it can be a source of hope. It means that the weak and vulnerable God accepts our weakness and vulnerability. It means that the cruel appearances of life are the lies, and that joy and grace are the deeper realities. It means that God is with us, that God is for us, even when we feel forsaken, especially when we feel forsaken. It means that our exiled souls can find a home in Bethlehem.